Antibiotic resistant bacteria cause an estimated 2 million infections and 23,000 deaths each year in the U.S., according to the Centers for Disease Control and Prevention.

Frequent and inappropriate use of antibiotics is a big culprit. Antibiotics can save lives when prescribed for a bacterial infection, but they won't help someone who has a viral infection.

Researchers at the University of Rochester Medical Center are working on a tool that could one day help doctors quickly determine which type of virus patients have.

"The usual way we traditionally have looked for causes of infection is to detect the pathogen,” said Ann R. Falsey, M.D., lead study author and interim chief of the Infectious Diseases Division at Strong Memorial Hospital. “This is different; it's not looking for the pathogen anymore, but the footprint it leaves behind."

A team of scientists at the UR-based Respiratory Pathogens Research Center has identified 11 genetic markers in blood that can distinguish between viral and bacterial infections. The markers correctly identified the pathogen 80 to 90 percent of the time in a study of 94 adults who were hospitalized with lower respiratory tract infections.

"Which is pretty good”, Falsey said. “We're more concerned about sensitivity than specificity because the default is to give everybody antibiotics. More simply put, we would rather over treat just a few people at this stage than not treat someone with a bacterial infection."

Falsey has received $50,000 in funding from the National Institutes of Health to continue the research and develop a prototype diagnostic test that could be used in hospitals and doctors’ offices. “We think we have some more work to do,” she said. “It's not quite ready for prime time yet."

The next phase of research, Falsey said, will need to focus on a larger sample size because the genetic classifiers selected from patients in the original study may not prove to be universal in all patients. For instance, those with asthma or emphysema may have a different host response to infection and should be examined separately.

The project is one of 10 semifinalists chosen from 74 submissions in a national competition to combat the development and spread of drug resistant bacteria. Falsey said a marketable blood test could be five to ten years away.